Further improved reversing flow catalytic converter for internal combustion engines

ABSTRACT

A further improved compact reversing flow catalytic converter with protection from overheating includes an improved valve unit which directs exhaust gases through a container filled with catalytic material to permit a bypass of catalytic material when a temperature of the material exceeds a predetermined threshold. The container defines a U-shaped gas passage that communicates with two chambers at the top of the container. The improved valve unit is mounted to the top of the container and includes two container chamber extension cavities, an improved intake cavity and an improved exhaust cavity. The improved valve unit includes an improved valve flapper and two conjoined valve walls each wall with two openings therethrough. The improved valve flapper rotates around normal central axis between a first, a second and third positions. When overheating of the catalytic material is predicted, a controller relinquishes control of the improved valve flapper and an improved center return mechanism rotates the improved valve flapper to a third position, in which each of the valve openings communicates with both inlet and exhaust ports so that the exhaust gas flow bypasses catalytic material. A fuel injection system under control of the controller is used so that measured amounts of fuel can be injected into the container reaction core to enhance oxidation. The catalytic material is thus protected from damage due to overheating. The advantage is a compact, reliable, highly efficient further improved catalytic converter that is inexpensive to manufacture, durable, and adapted for extended service life. The improved valve may driven by a stepper motor that moves and holds the valve to its three positions including bypass, forward and reverse flow. An alternate version also replaces the oxidizing flow-through monolith with an oxidizing filter trap.

The present invention relates to catalytic converters for internalcombustion engines, and in particular, to a further improved reversingflow catalytic converter over that disclosed in U.S. patent applicationSer. No. 11/218,608 filed Aug. 29, 2005 in the name of some of theinventors herein for treating exhaust gases from internal combustionengines.

BACKGROUND OF THE INVENTION

A problem relating to catalytic converters for internal combustionengines, such as the prior art reversing flow catalytic converter forinternal combustion engines disclosed in U.S. Pat. No. 6,148,613, isoverheating Lean burn combustion systems for fuel-efficient vehicles areparticularly hard on exhaust after-treatment systems because excessiveoxygen is always present in the exhaust. For example, the exhaust ofdiesel dual fuel (DDF) engines, which is one type of diesel engine,normally contains more than 5% volumetric oxygen after combustion. Underpartial load the surplus of oxygen in the exhaust may be higher than 10%by volume. Under such circumstances, any engine management problems thatresult in excessive fuel in the exhaust, will generally damage exhaustafter-treatment system due to overheating.

If a fuel management problem occurs, a large amount of the excess fueldelivered to the engine can pass through it and into the engine exhaust.That fuel will burn inside the catalyst if sufficient oxygen isavailable and the catalyst has reached catalytic temperature. Forexample, the complete burning of 2% of methane in the exhaust, can raisethe temperature of exhaust gases by about 420° C., in addition to the600° C. temperature of the exhaust as it is ejected from the engine.Consequently, the rate of temperature rise in the catalyst can reach 20to 30° C./second, if the monoliths are metallic. Besides the catalyticburning of methane, any combustible matter such as soot accumulated onthe catalyst surface, will also be rapidly oxidized under such hightemperatures. The burning of accumulated soot will escalate and prolongthe temperature rise. The thermal wave oscillation produced by thereverse flow process will also expedite the rise of the peak temperatureof the catalyst substrate. Once the catalyst temperature reaches 1200°C., a metallic substrate will begin to soften and subsequently losemechanical strength. Further temperature rise will cause collapse of thesubstrate and eventual melt-down will occur when it is heated to1400-1450° C. A detrimental uncontrolled temperature rise can damage acatalyst in less than 20 seconds.

In the prior art, when a catalyst protection mode is required for agasoline engine, an extremely rich fuel/air mixture is delivered to theengine. Since all oxygen is basically consumed inside the engine duringthe over-rich combustion process, the engine exhaust contains no oxygen.The large amount of excessive fuel from the engine pulls down thecatalyst temperature. In this type of catalyst protection mode, however,the carbon monoxide content of the exhaust gas is undesirably very high.

However, for lean burn systems such as diesel or dual fuel engines, theexcessive fuel will not cool down the catalyst temperature because ofthe presence of a high concentration of oxygen in the exhaust.Furthermore, lean burn systems cannot burn stoichiometric fuel/airmixtures because of knocking restrictions. For knock-free operation of adual fuel engine, the original compression ratio of the baseline dieselengine requires the pre-mixed natural gas/air mixture to be generallyleaner than λ=1.5.

As well, the concept of the reversing flow catalytic converter has beenfound to offer nearly continuous oxidation of exhaust components, mainlyunburned hydrocarbons and carbon monoxide, when used after natural gasor dual fuel engines, in a 13 mode test cycle. For this reason, such acatalytic converter will likely not require supplementary heat added tothe converter to maintain oxidation temperature. However, for a dieselengine there are fewer hydrocarbons and CO in the exhaust streamproviding less fuel in the emissions. Engine fuel will need to be addedto the exhaust stream during idle and low power operation of the enginein order to maintain an oxidation temperature sufficient to convert COand hydrocarbons (including particulates), however, a considerablylesser amount of fuel than would be required by a conventionaluni-directional oxidation catalyst. For this reason, addition of fuelcan also result in overheating of the catalyst, if too much fuel isadded.

U.S. Pat. No. 6,148,613 discloses a prior art reversing flow catalyticconverter for internal combustion engines. Such device 10 includes avalve housing 14 which reversibly directs exhaust gases through a “U”shaped passage having a catalytic material therein. A valve disk 42having two openings 48 therein rotates around a central axis, wherein ina first position of such rotatable valve disk 42 the exhaust gases enterthe exhaust cavity from an exhaust pipe and pass through one of theopenings in valve disk 42 into the “U” shaped passage. In the secondposition of the rotatable valve disk 42, the disk 42 and correspondingopenings 48 therein are rotated 90° so that each opening 48 communicateswith the same cavity within the valve housing 14, but a different one ofthe ports communicating with the U-shaped passage, so that gas flowthrough the u-shaped passage is thereby able to be reversed.

Disadvantageously, prior art devices such as the type disclosed in U.S.Pat. No. 6,148,613 lack a safeguard system to protect such reversingflow catalytic converter from overheating, as may arise under any one ormore of the conditions explained above.

Further, there exists a need for a continuously oxidizing filterparticulate trap for diesel engine exhausts.

An improved patent application Ser. No. 11/212,608 addresses the aboveproblems and disadvantages and presents solutions and improvements.

The improved patent however, suffers from use of a rotating compactvalve that is prone to having a high degree of friction drag due to itsdesign and requirement for low leakage of exhaust gas across the valve.For each percent of exhaust gas leakage across the valve, theeffectiveness of the destruction of exhaust methane or exhaustparticulates diminishes by about one percentage point. Leakage and dragat the valve are reduced in this new invention by a re-configuration ofthe valve rotor and stator ports from being rotated as a slidingassembly perpendicular to and rotated about a shaft, to the rotor nowbeing a symmetrical flapper and four stator ports now being fixed in thetwo conjoined inner valve walls parallel to the shaft intersecting eachother at the center of the valve at the shaft area, and the rotorflapper being rotated about the shaft between two stator walls with fourports. The improved valve is divided into four cavities separated fromeach other by the internal valve walls The valve cavities extending fromcontainer chambers one and two and constrained between valve bottomports one and two, the two valve inner walls, the outer wall and thecover plate are now better described as extended cavities to chambersone and two of the container. The valve cavities extending from theinlet and outlet piping ports and constrained by the valve top andbottom covers and between two valve walls are now better called inletand outlet cavities through which the flapper moves to redirect flow asdirected by the controller, actuator, spring return and rotor The rotoris now better described as a symmetrical flapper without ports and thestator is now better described as two pairs of conjoined wallsintersecting at the center of the valve housing, each wall sectionhaving a valve port which the flapper covers two at a time while leavingthe other two completely uncovered on a cyclic basis This type of valveaction occurs with very little drag even at operating temperature, andthe flapper is able to cover valve ports effectively and in this mannerimprove exhaust component destruction efficiency. The valve action ofthe flapper alternately covering two ports and uncovering the other twoports on a cyclic basis, is controlled by a temperature control systemand has the effect of reversing the flow of exhaust gas cyclicallyflowing through the monolith in the container.

The improved patent application also suffers from a neutralizing springreturn design with two compressed springs such that the spring return isnot force-balanced at the shaft and therefore prone to shaft wear.Therefore an improvement is made to create a force-balanced springreturn with the use of four compressed springs mounted in such a way asto balance out forces on the shaft that were prevalent with the originaltwo spring design.

The improved patent application used diesel injection as required intothe inlet pipe taking exhaust gases from the diesel engine into thevalve and oxidation or filter monolith and also mentioned that injectionof diesel was alternately possible into the space at the central core ofthe monolith. It is preferred to add diesel fuel within the central coresince the heat in this area is prevalently greater than in the inlet tothe monolith, giving greater opportunity for complete dieselvaporization within the core thereby effecting a greater oxidationefficiency of the added fuel.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide afurther improved reversing flow catalytic converter system for treatingexhaust gases from an internal combustion engine, which system includesan improved compact valve structure incorporated in the converter aswell as an improved safeguard system to protect the catalyst andconverter from overheating and including an improved method for monolithheat addition by diesel injection into the central core of the monolith.

Another object of the present invention is to provide a further improvedreversing flow catalytic converter system for treating exhaust gasesfrom an internal combustion engine which has a compact structure forefficient performance, minimal heat loss, and mechanical simplicity.

Yet another object of the present invention is to provide an improvedthree-way valve for a further improved reversing flow catalyticconverter which overcomes the shortcomings of the prior art discussedabove.

A further object of the present invention is to provide a furtherimproved reversing flow catalytic converter having an improved bypasssystem to protect the further improved reversing flow catalyticconverter from overheating.

A still further object of the present invention is to provide animproved three-way valve for a further improved reversing flow catalyticconverter that is maintained in a neutral position to permit exhaustgases to bypass the further improved catalytic converter when theimproved valve is not actuated.

A further object of the present invention is to optionally provide afurther improved reversing flow catalytic converter with an oxidizingfilter trap that may or may not be coated with catalytic material, totrap, hold and oxidize particulates, in place of the oxidation catalyticsubstrate within the further improved reversing flow catalyticconverter.

A further object of the present invention is to provide a furtherimproved reversing flow catalytic converter with an improved means ofinjecting a controlled amount of diesel engine fuel within the core ofthe further improved reversing flow catalytic converter, when requiredto maintain a continuous oxidation temperature. The catalytic convertermonolith may or may not be coated with catalytic material, depending onthe application and upon the amount of fuel normally present in theexhaust stream and additionally injected into the middle of the furtherimproved reversing flow catalytic converter.

A still further object of the present invention is the provision of animproved force-balanced spring return design component such that theimproved valve can be reliably and quickly returned to a neutral orbypass position upon detection of damaging impending temperatures withinthe monolith of the further improved reversing flow catalytic converter.

Accordingly, in one broad aspect of the invention, a further improvedreversing flow catalytic converter for treating exhaust gases from aninternal combustion engine is provided, comprising:

-   -   a container having a gas flow passage therein and a top end        having a first chamber and a second chamber that respectively        communicate with the gas flow passage;    -   a catalytic material in the gas flow passage adapted for        contacting the exhaust gases that flow through the gas flow        passage;    -   an improved valve for reversing an exhaust gas flow through the        gas flow passage, including an improved valve housing with two        extended valve cavities connecting to chambers one and two of        the container and mounted to the top end of the container, an        improved intake cavity and an improved exhaust cavity, the        improved intake cavity adapted for connection to an exhaust gas        pipe from said engine and the improved exhaust cavity adapted        for connection to a tail pipe for egress of said exhaust gas        from said converter; and    -   an improved valve component for reversing gas flow operably        mounted to the improved valve housing, adapted to move between a        first position in which the intake cavity communicates with the        first valve opening and container chamber and the exhaust cavity        communicates with the second valve opening and container        chamber, a second position in which the intake cavity        communicates with the second valve opening and container chamber        and the exhaust cavity communicates with the first valve opening        and container chamber, and a third position which allows the        intake cavity to communicate with the exhaust cavity; and    -   a controller for controlling movement of the improved valve        component between the first and second positions during normal        operating temperatures for the further improved reversing flow        catalytic converter and otherwise permitting movement of the        improved valve component to the third position for abnormal        operating temperatures.

Alternatively, in another aspect of such first aspect, the presentinvention comprises a further improved reversing flow catalyticconverter for treating exhaust gases from an internal combustion engineis provided, comprising:

-   -   a container having a gas flow passage therein and a top end        having a first chamber and a second chamber that respectively        communicate with the gas flow passage;    -   a catalytic material in the gas flow passage adapted for        contacting the exhaust gases that flow through the gas flow        passage;    -   an improved valve for reversing an exhaust gas flow through the        gas flow passage, including an improved valve housing with a        bottom plate mounted to the top end of the container and        containing two openings, one connecting to each of the first and        second container chambers, and extended valve cavities within        the valve connecting the container chambers to an improved        intake cavity and an improved exhaust cavity, separated from the        container chambers and associated extended valve cavity by two        conjoined walls intersecting at the center of the valve housing,        each wall section having an opening that allows communication        between the container first and second chambers and connected        extended valve cavities and the intake and exhaust cavities when        the valve flapper is positioned to allow such communication. The        improved intake cavity is adapted for connection to an exhaust        gas pipe from said engine and the improved exhaust cavity is        adapted for connection to a tail pipe for egress of said exhaust        gas from said converter; and    -   an improved valve component for reversing gas flow operably        mounted to the improved valve housing, adapted to the be moved        between a first position in which the improved intake cavity        communicates with the first chamber of the container through the        first extended valve cavity and the improved exhaust cavity        communicates with the second chamber of the container through        the second extended valve cavity, a second position in which the        improved intake cavity communicates with the second chamber of        the container through the second extended valve cavity and the        improved exhaust cavity communicates with the first chamber of        the container through the first extended exhaust cavity, and a        third position which allows the improved intake cavity to        communicate with the improved exhaust cavity; and    -   a controller for controlling movement of the improved valve        component between the first and second positions during normal        operating temperatures for the further improved reversing flow        catalytic converter and to the third position to permit bypass        of exhaust gas without passing through said catalyst material        during certain other temperatures for the further improved        reversing flow catalytic converter.

Preferably, the improved valve housing has an interior cavity with twoopenings in the bottom plate and two transverse walls that divide thecavity into four parts, two parts that, with the outer wall and coverplate, respectively form cavity extensions of the container chambers oneand two, and the other two parts that respectively connect to the engineexhaust valve inlet pipe and the engine tailpipe outlet pipe Theimproved valve component may include a flapper plate which issymmetrical and rotatably mounted to the center of the valve housing atthe shaft, and rotates about a central axis that is perpendicular to theimproved valve cover plate and the two openings therein that communicatewith one of the inlet and exhaust cavities. The improved valve bottomplate has a first opening and second opening therethrough whichcommunicate respectively with each of the two container chambers.

More preferably, the gas flow passage is formed within an interiorchamber of the container, the interior chamber being separated by atransverse plate into two parts which respectively form a first chambersection and a second chamber section. The two sections communicate witheach other, and each of the chamber sections communicates with one ofthe first and second valve openings. The container further comprises agas permeable material which contains the catalytic material. The gaspermeable material preferably comprises a plurality of monoliths havinga plurality of cells extending therethrough, the monoliths being coatedwith a catalytic material.

According to a second aspect of the present invention, there is provideda further improved reversing flow catalytic converter for exhaust gases,the converter comprising a container which has a top end with a firstchamber and a second chamber that are in fluid communication with eachother so that the exhaust gases introduced into one of the first andsecond chambers flow through a catalytic material in the container. Theimproved valve structure comprises an improved valve housing includingtwo openings in the bottom plate of the improved valve housing, openingone that connects to the first chamber of the container and opening twothat connects to the second chamber of the container and two extendedvalve cavities, one connected to container chamber one through improvedvalve opening one and the other connected to chamber two throughimproved valve opening two, and an improved intake cavity and animproved exhaust cavity. The improved intake and exhaust cavities areseparated from the container first and second chambers and theirassociated extended valve cavities by two conjoined walls that intersectat the center of the improved valve housing, each wall making two wallsections and each section containing one opening such that two of thefour openings are blocked by the flapper alternately as dictated by thecontroller. The improved intake cavity is adapted for connection of anexhaust gas pipe and the improved exhaust cavity is adapted forconnection of a tail pipe. An improved valve component is provided forreversing gas flow operably mounted in the valve housing. The improvedvalve is adapted to move the flapper between a first position in whichthe improved intake cavity communicates with the first container chamberthrough its associated extended valve cavity and the improved exhaustcavity communicates with the second container chamber through itsassociated extended valve cavity, and a second position in which theimproved intake cavity communicates with the second container chamberthrough its associated extended valve cavity and the improved exhaustcavity communicates with the first container chamber through itsassociated extended valve cavity. The improved valve structure furtherincludes an improved center return mechanism associated with theimproved valve component for moving the improved valve component to athird position in which the improved intake cavity communicates with theimproved exhaust cavity through the improved valve component when theimproved valve component is not actuated to move to one of the first andsecond positions. Alternatively, the third position may be achieved bypositive action of a controller and actuator.

According to a third aspect of the present invention, there is provideda further improved reversing flow catalytic converter for treatingexhaust gases from an internal combustion engine. The catalyticconverter includes a container having a gas flow passage therein and atop end having a first chamber and a second chamber which respectivelycommunicate with the passage. A catalytic material is provided in thegas flow passage and contacts the exhaust gases which flow through thepassage. The further improved catalytic converter has an improved valvefor reversing the exhaust gas flow through the gas flow passage,including an improved valve housing with an improved intake cavity andan improved exhaust cavity, and two extended valve cavities mounted tothe top end of the container. The improved intake cavity is adapted forconnection of an exhaust gas pipe and the improved exhaust cavity isadapted for connection of a tail pipe. The improved valve also includesan improved valve component for reversing gas flow, operably mounted inthe improved valve housing, and adapted to be moved between the first,second, and third positions.. In the first position, the improved intakecavity communicates with the first container chamber through itsassociated extended valve cavity and the improved exhaust cavitycommunicates with the second container chamber through its associatedextended valve cavity In the second position, the improved intake cavitycommunicates with the second container chamber through its associatedextended valve cavity and the improved exhaust cavity communicates withthe first container chamber through its associated extended valvecavity. In the third position, the improved intake cavity communicateswith the improved exhaust cavity. A controller controls movement of theimproved valve component between the first and second positions, andmovement of the improved valve component to the third position, ifrequired to protect the catalytic material from overheating.

According to a fourth aspect of the present invention, a safeguardsystem is provided to inhibit overheating the further improved reversingflow catalytic converter. In addition to controlling the improved valvecomponent for reversing flow bypass operation, the controller is alsoadapted to indirectly control fuel supply to the engine, in order toprotect the catalytic material from overheating.

According to fifth aspect of the invention, there is provided a methodfor preventing overheating of the further improved reversing flowcatalytic converter. The further improved reversing flow catalyticconverter includes an improved valve adapted for connection of anexhaust gas pipe and a tail pipe, and associated with first and secondports of a container and their respective associated extended valvecavities for reversing exhaust gas flow through a catalytic material inthe container. The method comprises steps of monitoring temperatures ofthe catalytic material, and controlling an improved valve mechanism topermit the exhaust gases to flow from the exhaust gas pipe to the tailpipe without passing through the catalytic material when the temperatureof the catalytic converter exceeds a predetermined threshold. The methodalso preferably includes steps of calculating the rate of temperaturerise in the catalytic material, and controlling the improved valvemechanism to permit the exhaust gases to flow from the exhaust gas pipeto the tail pipe without passing through the catalytic material when therate of temperature rise exceeds a predetermined threshold. A furtheroptional step adjusts engine operation to reduce total hydrocarbon andcarbon monoxide volume in the exhaust gas flow.

The safeguard system in accordance with the present invention, protectsthe catalytic material from overheating when an abnormal rate oftemperature rise is detected. The bypass of exhaust gases around thecatalyst is the primary safeguard mechanism. During bypass, the exhaustgases do not flow through the monoliths in the catalytic converter.Thus, the inner catalyst is shielded from the flow of the fuel-oxygenmixture contained in the engine exhaust. Extensive testing has shownthat once the exhaust flow to the catalyst is stopped by the improvedbypass mechanism, the catalyst center temperature comes down quicklyeven if the exhaust gases are rich in both fuel and oxygen. However, ifoverheating occurs, the engine fuel supply is preferably adjusted toreduce the total hydrocarbon and carbon monoxide volume in the exhaust,as well as the temperature of the exhaust gases. In bypass mode, exhaustgases rich in fuel and oxygen will burn in the improved valve housing ifthe temperature of the improved valve housing is high enough The hightemperature resulting from the burning of the fuel in the improved valvehousing retards cooling of the catalyst, and may damage the improvedvalve structure. Therefore, control of the fuel supply is preferablewhen overheating occurs. Besides, in the bypass mode, the exhaust gasesare not treated by the catalyst and therefore, the concentrations ofhydrocarbons and carbon monoxide in the exhaust gas generally increases.

According to a sixth aspect of the invention, there is provided anoption to replace the oxidation catalyst within the further improvedreversing flow catalytic converter with a catalytic filter trap. In thisvariation of the reversing flow catalytic converter, a method isprovided to entrap particulates and to hold them for a period of time toallow effective oxidation of the particulate matter when the trap isheld at a continuous oxidation temperature by the temperature monitoringand control system. In this sixth aspect and as a second option, theoxidation catalyst may be replaced by a filter monolith that is notcoated with catalyst.

According to a seventh aspect of the invention, there is provided amethod by which diesel engine fuel may be injected through an injectorvalve that provides vaporized engine fuel into the central area of thefurther improved reversing flow catalytic converter within the flowredirection bowl. Diesel engine fuel passes into the flow redirectionbowl through a bulkhead fitting into a coiled small diameter tubingsection that provides sufficient heating surface to vaporize diesel fuelcomponents into the flow redirection bowl. Diesel fuel is provided tothe bulkhead fitting from a connecting pipe that connects a diesel fuelsupply manifold that in turn receives diesel fuel supply from the highpressure diesel injector low pressure supply pump. The manifold containsthe diesel injector, an associated flow orifice to control diesel flow,an associated check valve to block diesel flow during air purge and anassociated strainer to filter diesel fuel within the manifold blockbefore the injector. The manifold also contains an air injectionsolenoid valve that purges diesel fuel from the line downstream of thediesel injector by briefly injecting vehicle air into the dieselinjection line when the engine is shut down. The method comprises ofsteps of monitoring temperature of the monolith material and controllinga fuel injector valve mounted on the flow redirection bowl of thefurther improved reversing flow converter to inject metered quantitiesof fuel required to maintain a preset oxidation temperature of themonolith material. The method includes the provision of a controlinterlock such that in the event of overheating for any reason, thepower to the fuel injector valve will be locked out until the overheatcondition is removed. Additionally, when an overheat event occurs, theengine fuel supply will be adjusted to reduce total hydrocarbons andcarbon monoxide volume in the exhaust.

According to an eighth aspect of the invention, there is optionallyprovided, a three position valve and rotary stepper motor actuator whichincludes valve positions for; forward, reverse and bypass flow. In thisaspect, the valve position is determined by a pneumatic or electricstepper motor that is driven by a control method similar to thatdescribed earlier for the reverse flow oxidizing catalytic converter,comprised of steps of monitoring temperature and rate of temperaturerise of the oxidizing filter trap and controlling valve position suchthat exhaust gases are permitted to flow from the engine to the tailpipe without passing through the oxidizing filter trap when thetemperature of the monolith exceeds a predetermined threshold. This isthe third or bypass valve position

Other features and advantages of the invention will be more clearlyunderstood with reference to the preferred embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described by way of example only, andwith reference to the accompanying drawings, in which:

FIG. 1 is a side elevation view of the further improved reverse flowcatalytic converter of the present invention which includes an improvedbypass mechanism to control overheating of the catalytic material in thecatalytic converter, an improved valve to operate with low drag and lowleakage and an improved diesel fuel injection system;

FIG. 2 is a cross-sectional plan view taken along line A-A of theactuator 202 of FIG. 1 to show the structure of a rotary actuator fordriving the valve;

FIG. 3 a is a cross-sectional plan view taken along line B-B of theimproved bypass mechanism 316 of FIG. 1 to illustrate an improved centerreturn mechanism in a first position corresponding to that of theactuator shown in FIG. 2, and in dashed lines in a second positioncorresponding to a second position of the actuator shown in dashed linesin FIG. 2;

FIG. 3 b is a cross-sectional plan view taken along line B-B of theimproved bypass mechanism 316 of FIG. 1 to illustrate an improved centerreturn mechanism in position for bypass mode corresponding to theactuator neutral position shown in dashed lines in FIG. 2;

FIG. 4 a is a top plan view of the improved valve housing 301, showingthe inlet and outlet piping with flanges and the actuator and improvedspring return in a stack mounted at the center of the improved valve topcover plate.

FIG. 4 b is a elevation view of the improved valve housing 301, showingthe inlet and outlet piping with flanges and the actuator and improvedspring return stack mounted on the improved valve top cover.

FIG. 4 c is a bottom plan view of the improved valve housing 301 showingthe improved valve bottom plate and its two openings to communicate withthe two container chambers.

FIG. 5 a is an elevational view of the oxidation catalyst or filtercatalyst monolith of the further improved reverse flow catalyticconverter showing the monolith and transverse separation wall of theinlet section of the can in dashed lines.

FIG. 5 b shows the can top plan view of the can and monolith 302(section E-E of FIG. 1) and FIG. 5 c shows the bottom plan view of thecan and monolith 302.

FIG. 6 a shows the flow re-direction bowl 303 in elevational view withcapillary tubing shown in dashed lines.

FIG. 6 b shows the flow re-direction bowl 303 from its top plan view(section G-G of FIG. 1) showing the diesel injection capillary tubingand bulkhead fitting as well as an RTD mounted within the bowl.

FIG. 6 c is a schematic showing the injection manifold 347 with itsassociated flow components.

FIG. 7 is a cross-sectional plan view (section C-C of FIG. 1) of theimproved valve housing 301 with inlet and outlet openings in the valvecover plate superimposed in dashed lines and the flapper shown coveringtwo wall ports.

FIG. 8 a is an elevational cross-sectional view (section H-H of FIG. 7)showing wall sections 350 and 351 within the improved valve structurehousing 301 in a first direction.

FIG. 8 b is an elevational cross-sectional view (section J-J of FIG. 7)of the flapper 348 mounted within the improved valve structure housing301 in a second direction.

FIG. 8 c is an elevational cross-sectional view (section K-K of FOG. 7)showing wall sections 352 and 353 within the improved valve structurehousing 301 in a second direction.

FIG. 9 a is a bottom diagrammatic plan view of the bottom of theimproved valve 301 showing exhaust flow paths for one position of theimproved valve flapper in which exhaust gas from the engine enters thebottom inlet pipe and is redirected to the right hand side bottom platevalve opening and into the monolith and the flow that leaves themonolith enters the valve through the left hand opening of the improvedvalve bottom plate and is directed into the valve exhaust piping to thetail pipe. FIG. 9 b is a similar improved valve 301 bottom view showingthe flapper in the second position redirecting engine exhaust flow intothe monolith on the left hand side and out of the monolith on the righthand side and into the valve exhaust opening into the tail pipe. FIG. 9c is a similar bottom plan view of the improved valve 301 with theflapper in the bypass position allowing direct communication from theengine exhaust to the tail pipe directly through the valve and bypassingthe monolith.

FIG. 10 is a schematic plan for the control system 262 employed by thefurther improved reversing flow catalytic converter 300.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a further improved catalytic converter 300 inaccordance with an embodiment of the present invention whichincorporates a safeguard system to inhibit overheating the catalystmonoliths, an improved valve assembly, an improved spring return and animproved monolith can and re-direction bowl with improved diesel fuelinjection.

With reference to FIG. 1, the catalytic converter 300 comprises aimproved container 302 and improved valve housing 301 with a similarfunction as described in U.S. patent application Ser. No. 11/212,608. Arotary actuator 202 and a center return mechanism 316 are mounted on thedrive shaft 50 of the valve flapper parts 348 and 349. The rotaryactuator 202 is controlled to periodically rotate the valve flapperparts 348 and 349 between the first and the second positions to reversegas flow through the container 302.

As shown in FIG. 2, the rotary actuator 202 includes a housing 206 whichencloses a pressure chamber 208. A moveable vane 210 is mounted to driveshaft 212 which is adapted to be connected to the shaft 50 of the valveflapper parts 348 and 349 to rotate together therewith. The housing 206has a first opening 214 and a second opening 216 in the respective sidewalls of the housing 206 so that the moveable vane 210 rotates clockwiseuntil it abuts a left stop member 218 when pressurized fluid is injectedinto the pressure chamber 208 through the first opening 214. Thisposition of the moveable vane 210 corresponds to the first position ofthe valve flapper parts 348 and 349 as shown in FIGS. 7 and 9 b, topermit the exhaust gases to flow through the container in a firstdirection. Similarly, the moveable vane 218 rotates counter clockwiseuntil it abuts a right stop member 220, as shown in broken lines at theright side, when the pressurized fluid is injected into the pressurechamber 208 through the second opening 216. This position corresponds tothe second position of the valve flapper parts 348 and 349, as shown inFIG. 9 a, to permit the exhaust gases to flow through the container 302in the opposite direction.

As shown in FIGS. 3 a and 3 b, the center return mechanism 316 includesa base block 323 having a circular bore 321 at an apex of triangularcavities 324 and 325. A swivel arm 322 is connected on both ends to apivot shaft 358 that is rotatably mounted in the bore 321 of the baseblock. Four coil springs 317,318,319 and 320 are retained in the annulargrooves 359 and 360, each is restrained between one end of the grooves359 and 360 and one side of the swivel arm 322. A connector (not shown)is integrally formed with the pivot shaft 358, having a squarecross-section adapted to receive a square top end of pivot shaft 212(notshown) of the rotary actuator 202. The swivel arm members 322 areadapted to swivel within the triangular cavities 324 and 325 andcompress two of the springs 317, 318, 319 and 320 as they swivel. Theother of the springs 317, 318, 319 and 320 are free to expand within theannular grooves. A cover 243 (not shown) is provided to retain theswivel arms 322 and springs 317, 318, 319 and 320 within the base block323. When the pressure vane 210 of the rotary actuator 202 is at theleft side, corresponding to the first position of the valve flapper 348shown in FIGS. 7 and 9 b, the swivel arm 322 of the center returnmechanism 316 compresses springs 317 and 318. When the pressure vane 210of the rotary actuator 202 pivots to the right side as shown in thebroken line at the right side of FIG. 2, the valve flapper parts 348 and349 are in the second position as shown in FIG. 9 a. However, when therotary actuator 202 is deactivated (no fluid pressure is applied toeither side of the pressure vane 210), the swivel arm 322 of the centerreturn mechanism 316 is forced by two of the springs 317 and 318, toreturn to the central position shown in FIG. 3b. This moves the pressurevane 210 of the rotary actuator 202 to the central position shown inbroken lines in FIG. 2. It also moves the valve flapper parts 348 and349 to the bypass position shown in FIG. 9 c.

FIGS. 4 a, 4 b and 4 c illustrate features of the improved valvehousing. FIG. 4 a is a plan view of the valve housing showing inletflange 312 and inlet pipe 313 receiving exhaust gas from a diesel engineand outlet pipe 315 and outlet flange 314 discharging purified exhaustgas to the vehicle tail pipe. FIG. 4 a also illustrates valve coverplate 310 and the two openings in the cover plate 329 and 328 allowinggas to pass into and out of the valve housing inlet and outletcompartments formed by valve interior walls 350, 351, 352 and 353 ofFIG. 7 FIGS. 4 a and 4 b also show improved spring return 316 andactuator 202 mounted to the valve cover 310 and to each other by abracket (not shown) and connected to shaft 50 that also connects toimproved valve flapper parts 348 and 349 of FIG. 7. FIG. 4 b also showsthe outer improved valve outer assembly consisting of outer wall 330that is welded to top flange 311 that fastens to valve cover plate 310and valve bottom flange 309 that also is welded to outer wall 330.

FIG. 4 c is is a bottom view cross-sectional along line D-D of FIG. 1showing the valve bottom plate 309 and its two ports 326 and 327 thatconnect to can chambers 333 and 334 of FIG. 5 b.

FIGS. 5 a, 5 b and 5 c illustrate the further improved reversing flowcatalytic converter can and substrate section 302. FIG. 5 a is anelevational view of the can and substrate section 302 including canupper and lower flanges 308 and 306 respectively attached to wallsection 331, and transverse wall section 335 in dashed lines andattached to flange 308 and wall 331 and sealed to the upper surface ofmonolith or substrate 336 surface also in dashed line. FIG. 5 a alsoshows the preferred mountings of resistance temperature detectors (RTDs)307, approximately ¼ and ½ of the way down the substrate on each side ofthe transverse wall and below the substrate 336 surface. FIG. 5 b is atop plan view of the can or cross-sectional vied along line E-E of FIG.1 showing the transverse wall 335 and the substrate 336 visible throughcan chamber openings 333 and 334. FIG. 5 c is a bottom can orcross-sectional view along line F-F of FIG. 1 showing the exposedsubstrate 336 mounted flush with bottom flange 306.

FIGS. 6 a, 6 b and 6 c illustrate the further improved reversing flowcatalytic converter flow re-direction bowl 303 and diesel fuel injectioncapillary tubing 337 as well as a schematic showing the diesel injectionblock 347 with its integral components. FIG. 6 a shows an elevationalview of the flow re-direction bowl 303 comprised of flange 305 and bowlcontainer 332. Also shown in FIG. 6 a is a tubing bulkhead fitting 304,internal coiled tubing 337 in dashed lines supported by a bracket (notshown) and RTD 307. FIG. 6 b is a plan view of cross-sectional areaalong line G-G of FIG. 1, showing flange 305 and bowl container 332,bulkhead fitting 304, coiled tubing 337 and RTD 307. The schematic shownin FIG. 6 c reveals the manifold block 347 with internally mountedcomponents; check valves 342, filter screen 340 and orifice 341. Adiesel supply from the diesel fuel supply pump 345 enters the manifoldblock 347, is filtered by screen 340 before passing to a diesel injectorvalve 339 that is under control of converter controller 262 of FIG. 10and then passing through a flow control orifice 341 and check valve 342and thence out of the manifold block into tubing leading directly tobulkhead fitting 304. The manifold block 347 also contains flow passagestha direct air from vehicle air supply 346 directly to air purgesolenoid 344 and then through check valve 343 and directly to tubingleading to bulkhead fitting 304. When the vehicle is shut down, theconverter controller 262 will de-activate diesel injection solenoid 339blocking diesel flow and briefly activate air purge solenoid 344sufficient to clear diesel fuel from the tubing leading to bulkheadfilling 304 and from capillary tubing 337 so that caking of the tubingis prevented.

FIG. 7 is a cross-sectional plan view along line C-C of FIG. 1illustrating the internal wall system consisting of walls 350, 351, 352and 353 that converge near the center of the valve and around valveshaft 50 that is connected to valve flapper sections 348 and 349. Theangles subtended by the wall system are about 60 degrees in thedirections of inlet opening 328 and outlet opening 329 in valve coverplate 311 and about 120 degrees in the directions of valve bottom plate309 openings 326 and 327 that connect to can cavities 333 and 334 ofFIG. 5 b. As shown in FIG. 7, valve flapper section 348 completelycovers the opening 354 of FIG. 8 a in wall 350 and valve flapper section349 completely covers the opening 356 of FIG. 8 c in wall 352.

FIGS. 8 a, 8 b and 8 c all illustrate cross-sectional elevations of theinternal improved valve structure of wall sections and flapper sections.FIG. 8 a shows the internal cross-sectional elevation along line H-H ofFIG. 7 displaying wall sections 350 and 351 and wall openings 354 and355 respectively. This view also shows top cover plate opening 329 thatconnects to the inlet pipe 313 and bottom plate opening 326 thatconnects to can inlet cavity 334 of FIG. 5 b. FIG. 8 b shows the valveinternal cross-sectional elevation along line J-J of FIG. 7 displayingthe flapper sections 348 and 349 with connected shaft 50 and wallsections 352 and 353 in behind the flapper sections and also showingwall openings 356 and 357 in dashed lines. In this illustration, theflapper section completely seals wall opening 356 in wall section 352and completely uncovers wall section opening 357 in wall section 353.FIG. 5 c shows the valve internal cross-sectional elevation along lineK-K of FIG. 7 displaying wall sections 352 and 353 along with wallsection openings 356 and 357 respectively. In the position of valveflapper sections 348 and 349 shown in FIG. 7, opening 356 of wallsection 352 is completely sealed by flapper section 349 and opening 357of wall section 353 is completely uncovered. With the valve flapperposition shown in FIG. 7, engine exhaust gases enter the valve housingthrough opening 329 and then through wall opening 355 of wall section351 and then through opening 326 of the valve bottom plate into cancavity 334 and into the oxidation or filter monolith 336 down the lefthand side in FIG. 5 b and then into the flow re-direction bowl 303 ofFIG. 6 a and then up and into the oxidation or filter monolith righthand side of FIG. 5 b and into can cavity 333 and then through valvebottom plate opening 327 and then through opening 357 of wall section353 and out of the valve housing through top valve cover opening 328.

FIGS. 9 a, 9 b and 9 c illustrate the valve flapper sections 348 and 349in their three positions, for respectively forward and reverse exhaustflow through the container 302 and for bypassing the oxidation or filtercatalytic material. For clearer illustration, these figures illustrateonly a bottom plan schematic view of the valve housing with valve bottomplate 309 removed exposing flapper sections 348 and 349, wall sections350, 351, 352 and 353 and valve inlet opening 329 and valve outlet 328.The four wall sections divide the interior cavity of the valve housing301 into the intake cavity and exhaust cavity, and into two other valvecavities that are essentially extensions of the two can cavities.

When the valve flapper sections 348 and 349 are in the first position asshown in FIG. 9 a, the gas flow enters intake cavity from the inletopening 329. The gas flow passes through the valve wall opening 355 inwall section 351 to enter the container through valve bottom plateopening 326 and disperse container cavity 334 and into the cells of thecatalytic material above within the container on the left hand side ofthe transverse wall 335. After the exhaust gas flow is forced throughthe catalytic material it exits on the opposite side of the containertransverse wall which is on the right hand side of the transverse wall335, and passes first through second container cavity 333 and thenthrough the valve bottom plate opening 327 to the exhaust cavity throughwall opening 357 in wall section 353. The gas flow then exits throughthe outlet opening 328.

As shown in FIG. 9 b, when the valve flapper sections are in the secondposition, it is rotated about 60° counter-clockwise so that the gas flowentering the intake cavity through the inlet opening 329 passes throughvalve wall opening 356 in wall section 352. Therefore the gas flow mustenter the container through the valve bottom plate opening 327 and firstmove into container cavity 333 and exit the container through containercavity 334 and then through valve bottom plate opening 325 and throughvalve exhaust opening 328 so that the gas flow in the container isreversed, in comparison to the gas flow shown in FIG. 9 a

If during the reversing flow operation of the further improved catalyticconverter 300, the temperature of the catalyst material rises tooquickly or is predicted to overheat the catalytic material, a controllerplaces the catalytic converter in bypass mode. In bypass mode, therotary actuator is deactivated by interrupting the pressurized fluidsupply (not shown) or electric power Supply. When the rotary actuator202 is deactivated, the swivel arm 322 of the improved center returnmechanism 316 is forced by two of the springs 317, 318, 319 or 320, toreturn to its central position as shown in FIG. 3 b. Thus, the centerreturn mechanism 316 moves the valve flapper sections 348 and 349 to thethird (bypass) position which is between the first and second positions,as shown in FIG. 9 c. The valve flapper sections 348 and 349 aremaintained in the third position until the rotary actuator 202 isreactivated. When the valve flapper sections 348 and 349 are in thethird position, the valve wall openings 354, 355, 356 and 357communicate with both the intake cavity and the exhaust cavity. Thus,the gas flow entering the intake cavity through the inlet opening 329passes directly through the valve wall openings, enters the valveexhaust cavity, and exits the valve outlet opening 328. Even though thevalve wall openings 354, 355, 356 and 357 communicate through the firstand second valve bottom plate openings 326 and 327 with the container,the gas flow through the valve wall openings does not enter thecontainer 302 because the gas pressure at the first valve bottom plateopening 326 is equal to the gas pressure at the second valve bottomplate opening 327. Thus, when the valve flapper sections 348 and 349 arein the third position, the exhaust gases bypass the container 302.

The further improved catalytic converter 300 described above withreference to FIGS. 1 through 9 c is preferably controlled by a controlsystem, a preferred embodiment of which is illustrated in FIG. 10.During normal engine operation and normal reverse flow catalyticconverter operation, a controller 250 monitors the temperature of thecatalytic material in the catalytic converter. Resistance temperaturedetectors (RTDs) 307 attached to the catalytic converter 302 and 303, orimbedded in the catalytic material, are preferably used to measuretemperatures of the catalytic material.

As long as the temperature measured is within a predetermined range, thecontroller controls the rotary actuator 202 to achieve cyclic reverseflow through the catalytic converter by periodically rotating valve 301so that the reverse flow valve 301 is moved between the first and secondpositions. If an abnormally sharp rise in temperature is detected, or ifthe temperature of the catalytic material rises above a threshold thatwill predictably damage the catalytic material, the controller 250enters the bypass mode. During the bypass mode, the controller 250deactivates the rotary actuator 202. When the rotary actuator 202 isdeactivated, the improved center return mechanism 316 forces the reverseflow valve 301 into the third position to cause the gas flow to bypassthe catalytic converter 302/303, as described above with reference toFIG. 9 c.

Exhaust flow bypass is a first safeguard action to prevent damage to thereversing flow catalytic converter. Adjusting engine fuel supply isanother. Therefore, when the controller enters bypass mode, it sends asignal to the engine controller 252. The engine controller responds tothe signal by adjusting the engine fuel supply to reduce totalhydrocarbon and carbon monoxide volume in the exhaust gases.

As seen in FIG. 10, an auxiliary catalytic converter 254 connected inseries to the engine exhaust system downstream of the reverse flowcatalytic converter 302/303 may be optionally installed During bypassmode, the controller 250 activates the valve 256 to direct the exhaustflow to pass through the auxiliary catalytic converter 254, which willoxidize at least a part of the carbon monoxide and hydrocarbons duringthe bypass mode. The auxiliary catalytic converter may be smaller andless expensive than the reversing flow catalytic converter 300.

A look-up table 258 may be accessed at the controller 250. The look-uptable 258 stores data defining a dynamic limit of a rate of rise of thetemperature of the catalytic converter 300. Each time the controller 250samples the temperature of the catalyst using the RTDs 307, thecontroller 250 calculates the dynamic rate of rise in the temperatureand compares the dynamic rate of rise in the temperature with entries inthe look-up table 258, to obtain an early indication of overheating inthe catalyst. The controller 250 must promptly respond to an indicationof overheating in the catalytic material. The more quickly thecontroller 250 responds to the prediction of overheating in thecatalytic converter, the better the catalyst is protected. A quickresponse will protect the washcoat from damage whereas a delayedresponse may only protect the monolith from meltdown. The control systemtherefore needs to be sensitive enough to protect the washcoat most oftime and invariably prevent meltdown of the monolith substrate. However,over-sensitivity will trigger catalyst protection when it is notrequired. Frequent triggering of unwarranted catalyst protection willcompromise engine performance in the case of engine management-systemsand unnecessarily increase emissions in the case where bypass protectionis used.

The control algorithm used by the controller 250 therefore determineswhen to enter bypass mode based on catalyst temperature thresholds.Appropriate setting of the temperature thresholds will safeguard thecatalyst from overheating provided there is a slow climb in catalysttemperature. However, static temperature thresholds are not sufficientto prevent the catalytic washcoat from damage if operating conditionscause a serious fuel management problem. Serious fuel managementproblems may result in a sustained rate of temperature rise over 20-30°C./second. Due to the inherent delay in temperature sensing andprocessing, and a slight delay in the response of the bypass mechanism,an early prediction of overheating is required to protect the washcoat.

It should be noted that only catalyst temperatures are used to predictoverheating by the control algorithm. The catalyst temperature and therate of temperature rise in the catalyst temperature are used by thecontrol algorithm. The engine exhaust temperature is not measured orconsidered, because exhaust temperatures vary at a much greater ratethan catalyst temperature variation during normal engine operatingconditions.

As an example, described below is a safeguard system for preventingoverheating of a reversing flow catalytic converter used for adiesel/natural gas duel fuel engine.

Three Type-K thermocouples were installed in the catalytic converter,one at each side of the boundary layers, that is, inside the catalystsubstrate, and a third one at the bottom center of the containerstructure. Type-K thermocouples are commonly used to measuretemperatures of 0° to 1250° C. in various industrial processes. Forbalancing control of a catalyst flow-path temperature profile, twoboundary thermocouples are preferred so that heat is measured moreefficiently. For catalyst overheat protection, the two boundarythermocouples and the central thermocouple are required to provide earlywarning of any fuel management faults. The control algorithm used by thecontroller 250 provides the system with the following functionality:

-   -   The reverse flow mode is terminated when all three thermocouples        measure catalyst temperatures lower than 300° C. When any one of        the three thermocouples measure a catalyst temperature higher        than 350° C., the reverse flow mode is turned on.    -   The controller continuously computes rates of temperature rise        in the catalyst and compares each computed rate of rise with        predetermined values in the look-up table 258. The controller        250 triggers the system into bypass mode if a rate of        temperature rise listed in the look-up table is exceeded by a        computed rate. After entering bypass mode, the reverse flow        catalyst converter is bypassed, as explained above. A prediction        that the catalyst is about to overheat also triggers the engine        controller 252 to switch to diesel mode. This shuts off the        natural gas fuel supply and causes the engine controller to        begin self-diagnostics. The engine controller 252 is also        preferably programmed to operate the engine in a special diesel        mode, in which the diesel injection timing is advanced as        compared to normal diesel mode in order to lower engine exhaust        temperature The reverse flow mode is resumed after the catalyst        has cooled down to a predetermined restart threshold, 580° C.,        for example. If each of thermocouples indicate temperatures that        are lower than the restart threshold, and a catalyst damage flag        has not been set, the reverse flow mode is resumed. The        controller 250 sets a damage flag when any one of the        thermocouples indicates a temperature that exceeds a temperature        that might damage the catalyst. If a damage flag is set, the        reverse flow mode is not resumed until the catalytic material        has cooled to temperature below a predetermined threshold.

The effectiveness of the safeguard system is ensured by multiplethresholds and the combination of static and dynamic temperaturetracking. A performance evaluation test for the safeguard system wasconducted to test the effectiveness of the catalyst temperature controland the durability of control functionality under a wide range of engineand vehicle operating conditions, including fuel management systemfailures. Evaluation tests demonstrated that the safeguard systemreliably activated each time the controller determined that protectionmode was required. For slow temperature rise, the onset of the bypassmode was triggered by either inlet or outlet catalyst temperaturereadings exceeding the static temperature threshold. Test results showedthat the onset of bypass mode almost immediately stopped monolithtemperature rise under slow temperature rise conditions. If an abnormalrate of temperature rise triggers bypass mode, the onset of bypass moderapidly reduces and subsequently reverses the temperature rise. Thetests indicted that the safeguard system reliably prevented meltdown ofthe catalyst under these conditions.

The protection of the catalyst washcoat is more difficult, mainlybecause of the narrow line between optimized working catalysttemperatures and washcoat damage temperatures. The catalyst testedworked best when bed temperatures were maintained between 580° and 640°C. and peaked at 720° C. Catalyst ageing is accelerated above 730° C.and reactivity deteriorated over 760° C. If high concentrations ofhydrocarbons are present in the exhaust gases, a flame may be sustainedin the valve housing for some time during bypass mode. Under suchcircumstances, the cavity of the valve housing is the hottest zone andconducts heat to the top of the monolith. However, the flame does notpropagate to the inside of the catalyst because bypass mode stops gasflow through the catalyst. Rapidly adjusting the engine fuel supplyprovides improved protection for the washcoat.

The monolith material 336 of FIG. 5 can be either an oxidation substrateor a particulate filter substrate with or without a catalyst washcoat..The replacement of the oxidation monolith with an oxidation particulatefilter trap in FIG. 5 monolith 336. When used with a diesel engine, theoxidizing filter trap will trap and hold particulate matter to alloweffective oxidation of the carbon kernel as well as the volatile organicfractions of the particulates.

In FIG. 6, the location and mounting of a fuel injection valve 339 isillustrated on a diesel injection manifold 347. For a dual fuel engine,it is not likely that supplementary fuel injection will be needed, butif it is deemed useful, the injector valve 339 will be one designed forgaseous fuel injection in time duration pulses. If the reverse flowoxidizing converter is to treat exhaust gases from a diesel engine, thenthe injector valve 339 will be one designed for diesel fuel injection asa fine mistor vapour. The injector valve 339 supply 345 and a manifoldblock 347 complete with filter 340, fuel flow control orifice 341 andcheck valve 342. The manifold block will also have an air purge systemmomentarily activated on engine shut down to clean out the diesel linesfeeding the converter. An air supply 346 is connected to the manifoldblock 347 along with a check valve 343 and air purge solenoid 344. Awiring harness for power to activate the injector valve 339 and airpurge solenoid 344 under command of the converter controller 250 shownin FIG. 10. Power will be applied to the injector valve 339 when thetemperature profile is insufficient for oxidation and power will belocked off the injector valve 339 when the controller 250 is reacting toan overheat event. It is preferable to install diesel injector valvemanifold diesel piping to bulkheads fitting 304 on the flow re-directionbowl 303. The air purge solenoid will normally not be activated and willonly be momentarily activated on engine shutdown sufficient to blow alldiesel fuel from the diesel injection circuit including coiled capillarytubing 337 within the flow re-direction bowl 303.

In the cases of both the oxidizing catalytic converter and the oxidizingcatalytic filter, it may be feasible to reduce the amount of catalyticloading and maintain temperature at oxidizing levels by the use ofincremental fuel injection by way of fuel injector valve 339. In thelimit, with sufficient exhaust fuel injection, catalytic coating may notbe required. The amount of catalytic material may be balanced againstthe amount of fuel consumed in a case by case assessment of eachapplication

The control schematic of FIG. 10 shows a means of diesel injection withreverse flow controller 250 that can be used for the oxidizing converteror for the oxidizing particulate trap reverse flow controller. When theRTDs 307 detect a monolith temperature moving downward and approachingthe catalytic light off temperature, the converter controller 250 willcommand the fuel injection valve 339 to pulse a metered volume of fuelinto the converter re-direction bowl through bulkhead fitting 304. Asthe temperature moves upward from the added heat of the oxidizing fuel,the controller 250 will monitor the rate of temperature rise, and ifbelow a selected threshold rate of rise, the controller will pulse morefuel into the converter. This action will continue until the monolithtemperature is detected to be sufficiently above catalytic light offtemperature to sustain continuous oxidation of particulate matter. Underconditions of catalyst overheat, the power to the fuel injector 339 willbe disconnected until the overheat event is over. The control algorithmearlier described will act on both static temperature measurements andrate of temperature rise calculations for the oxidizing filter monolithin the same manner as for the oxidizing flow through catalyst monolith.

The advantages of the further improved catalytic converter describedabove are apparent. No plumbing is required between the converter unitand the valve unit, which makes the catalytic converter compact andinhibits heat loss between the valve and the catalyst. The valve flapperis rotated about a perpendicular axis, which provides a smooth andreliable valve operation in a minimum of space. The unique arrangementof the monolith improves catalyst life and conversion performance. Andthe reversing exhaust gas flow ensures maximum efficiency of conversionby keeping the catalyst material uniformly heated and in addition smallincremental fuel additions help to increase catalytic activity forpollutant reduction. Furthermore, the safeguard system including theimproved spring return mechanism used with the catalytic convertereffectively safeguards the catalytic converter from damage due tooverheating and effectively improves catalyst life. An additionaladvantage is the ability of the reverse flow catalytic converter to beoptionally modified to work effectively and efficiently as a continuousoxidation particulate filter trap.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained. Variouschanges could be made in the above methods and constructions withoutdeparting from the scope of the invention, which is limited solely bythe scope of the appended claims.

1. A further improved reversing flow catalytic converter for treatingexhaust gases from an internal combustion engine comprising: a containerhaving a gas flow passage therein and a top end having a first chamberand a second chamber that respectively communicate with the gas flowpassage; a catalytic material in the gas flow passage adapted forcontacting the exhaust gases that flow through the gas flow passage; animproved valve for reversing an exhaust gas flow through the gas flowpassage, including an improved valve housing with an improved intakecavity and an improved exhaust cavity, mounted to the top end of thecontainer with extended cavities to container chambers one and twowithin the improved valve, the improved intake cavity adapted forconnection to an exhaust gas pipe from said engine and the improvedexhaust cavity adapted for connection to a tail pipe for egress of saidexhaust gas from said converter; and an improved valve component forreversing gas flow operably mounted to the improved valve housing,adapted to be moved between a first position in which the intake cavitycommunicates with the first container chamber through its associatedextended valve cavity and the exhaust cavity communicates with thesecond container chamber through its associated extended valve cavity, asecond position in which the intake cavity communicates with the secondcontainer chamber through its associated extended valve cavity and theexhaust cavity communicates with the first container chamber through itsassociated extended valve cavity, and a third position which allows theintake cavity to communicate with the exhaust cavity; and a controllerfor controlling movement of the improved valve component between thefirst and second positions during normal operating temperatures for thecatalytic converter and to the third to permit bypass of some exhaustgas without passing through said catalyst material during certain othertemperatures for the further improved catalytic converter.
 2. A furtherimproved reversing flow catalytic converter as claimed in claim 1wherein the improved valve housing comprises an enclosed cavity with twoports in a bottom thereof and two conjoined walls that divides thecavity into four compartments that respectively form the intake cavity,the exhaust cavity, a valve extension cavity to container chamber oneand a valve extension cavity to container chamber two.
 3. A furtherimproved reversing flow catalytic converter as claimed in claim 2wherein the improved valve component includes a flapper that issymmetrical and rotatably mounted to the improved valve housing by ashaft mounted at the openings in the center of the improved valve bottomand top cover plates thereof and rotates about a central axis that isnormal to the flapper, the flapper being constrained to rotating betweenthe improved valve walls that define the inlet and exhaust cavities,each wall having a first opening and second opening therethrough whichcommunicate respectively with one of the container chambers and itsassociated extended valve cavity in each of the first and secondpositions, and one of the intake and exhaust cavities.
 4. A furtherimproved reversing flow catalytic converter as claimed in claim 2wherein each of the first and second openings in the improved valvewalls uncovered by the flapper in the third position communicate withboth the intake cavity and the exhaust cavity so that the gas flow isnot forced through the catalytic material in the container.
 5. A furtherimproved reversing flow catalytic converter as claimed in claim 4wherein the flapper further comprises a drive shaft driven by anactuator means.
 6. A further improved reversing flow catalytic converteras claimed in claim 5 wherein the actuator is activated by thecontroller to rotate the flapper between the first and second positions,and said third position.
 7. A further improved reversing flow thecatalytic converter as claimed in claim 6 wherein the flapper returns toand is maintained in the third position when the actuator is deactivatedby the controller.
 8. A further improved reversing flow catalyticconverter as claimed in claim 2 wherein the gas flow passage is formedwithin an interior chamber of the container, the interior chamber beingseparated by a transverse plate that forms a first chamber and a secondchamber, the first and second chambers communicating with each other,and each of the chambers communicating with the first and second portsof the improved valve housing.
 9. A further improved reversing flowcatalytic converter as claimed in claim 8 wherein the catalytic materialis spaced below the first and second ports of the improved valve housingto form an empty chamber between the first and second ports and thecatalytic material, the empty chamber being divided by the transverseplate into two separate compartments beneath the first and second portsof the improved valve housing, respectively, the improved valve housingof the improved valve being mounted to the top of the container in anorientation so that the container transverse plate is normal to thediametrical line that bisects the angle formed by the two conjoinedimproved valve walls that form the inlet and exhaust cavities within theimproved valve housing.
 10. A further improved reversing flow catalyticconverter as claimed in claim 9 wherein the improved valve flapper ispositioned between the transverse walls of the inlet and exhaustcavities, the improved valve flapper being normal to both transversewalls, and each of the two openings in each of the valve walls issmaller than a half section of each of the first and second ports of thevalve bottom plate.
 11. A further improved reversing flow catalyticconverter as claimed in claim 10 further comprising a mechanism foraccurately positioning the improved valve on the top of the containerand removeably securing same.
 12. A further improved reversing flowcatalytic converter as claimed in claim 1 further comprising a sensordevice for measuring temperatures of the catalytic material.
 13. Afurther improved reversing flow catalytic converter as claimed in claim7 further comprising an improved center return mechanism associated withthe drive shaft of the flapper to maintain the flapper in the thirdposition, and adapted to be overridden by the actuator.
 14. A furtherimproved reversing flow catalytic converter as claimed in claim 13wherein the improved center return mechanism comprises of a four-springmechanism in which uneven spring forces produce a torque adapted torotate the drive shaft until the disk is in the third position.
 15. Asafeguard system for a further improved reversing flow catalyticconverter to inhibit overheating of a catalytic material used to treatthe exhaust gases from an internal combustion engine, the furtherimproved reversing flow catalytic converter including: a containerhaving a gas flow passage therein and a top end having a first chamberand a second chamber that respectively communicate with the passage; acatalytic material in the gas flow passage adapted to contact theexhaust gases which flow through the passage; and an improved valvemechanism for reversing an exhaust gas flow through the gas flowpassage, including an improved valve housing with an improved intakecavity, an improved exhaust cavity, an extended valve cavity to chamberone of the container and an extended valve cavity to chamber two of thecontainer, mounted to the top end of the container, the improved intakecavity adapted for connection to an exhaust gas pipe of said engine andthe improved exhaust cavity being adapted for connection to a tail pipeto permit egress of exhaust gases from said further improved converter,the improved valve mechanism further including an improved valvecomponent for reversing gas flow operably mounted to the improved valvehousing, the improved valve component being actuated by an actuator tomove between a first position in which the improved intake cavitycommunicates with the first chamber of the container through itsassociated extended valve cavity and the improved exhaust cavitycommunicates with the second chamber of the container through itsassociated extended valve cavity, and a second position in which theimproved intake cavity communicates with the second chamber of thecontainer and its associated extended valve cavity and the improvedexhaust cavity communicates with the first chamber of the containerthrough its associated extended valve cavity, the system comprising: atleast one temperature sensor for measuring a temperature of thecatalytic material in the container; and a controller for controllingmovement of the improved valve component between the first and secondpositions.
 16. A safeguard system as claimed in claim 15 which providesfor the movement of the improved valve component to a third position inwhich the exhaust gas flow bypasses the catalytic material in thecontainer.
 17. A safeguard system as claimed in claim 16 wherein thecontroller is adapted to activate the actuator to rotate the improvedvalve component for a normal reversing flow operation when thetemperature of the catalytic material is above a first predeterminedthreshold.
 18. A safeguard system is as claimed in claim 17 wherein thecontroller is adapted to activate the actuator and resume normalreversing flow operation when the temperature of the catalytic materialdrops below a second predetermined threshold.
 19. A safeguard system asclaimed in claim 16 further comprising an improved center returnmechanism for moving the improved valve component to and maintaining theimproved valve component in the third position when the controllerdeactivates the actuator.
 20. A safeguard system as claimed in claim 19wherein the controller is adapted to deactivate the actuator to stop thenormal reversing flow operation and send a signal to an enginecontroller to adjust the fuel supply to the engine when a rate of riseof the temperature of the catalytic material is higher than apredetermined threshold retrieved from a look-up table.
 21. A safeguardsystem as claimed in claim 20 wherein the controller is adapted todeactivate the actuator to stop normal reversing flow operation and senda signal to an engine controller to adjust the fuel supply to theinternal combustion engine when the temperature of the catalyticmaterial exceeds a third predetermined threshold.
 22. A safeguard systemas claimed in claim 21 further comprising an auxiliary catalyticconverter connected thereto for treating the exhaust gases only when theexhaust gases bypass the further improved reverse flow catalyticconverter.
 23. A method for preventing overheating of a catalyticmaterial in the further improved reversing flow catalytic converterwhich is used for treating exhaust gas from an internal combustionengine which further improved converter includes an improved valve forcontrolling an exhaust gas flow through a catalytic material in thecontainer, the method comprising: monitoring a temperature of thecatalytic material; and controlling the exhaust gas flow to bypass thecatalytic material when the temperature of the catalytic material ispredicted to cause overheating of the catalytic material.
 24. A methodas claimed in claim 23 further comprising a step of: periodicallymeasuring the temperatures of the catalytic material; periodicallycalculating a rate of rise of the temperature of the catalytic materialusing the temperatures measured; and controlling the exhaust gas flow tobypass the catalytic material when the rate of rise of the temperatureof the catalytic material exceeds a pre-determined threshold.
 25. Amethod as claimed in claim 24 further comprising a step of: adjustingengine operation to reduce oxidyzable components in the exhaust gaseswhen the rate of rise of the temperature of the catalytic materialexceeds the predetermined threshold
 26. A method as claimed in claim 25further comprising a step of: adjusting engine operation to reduce totalhydrocarbon and carbon monoxide volume in the exhaust gases when therate of rise of the temperature of the catalytic material exceeds thepredetermined threshold.
 27. A method as claimed in claim 24 wherein thepredetermined threshold of the rate of rise of the temperature isdetermined by comparing a rate of temperature rise of the catalyticmaterial and an instant temperature of the catalytic material withcorresponding entries in a look-up table.
 28. A method as claimed inclaim 23 further comprising a step of: adjusting engine operation toreduce total hydrocarbon and carbon monoxide volume in the exhaust gaseswhen the rate of rise of the temperature of the catalytic materialexceeds the predetermined threshold.
 29. A method as claimed in claim 23further comprising a step of: directing the exhaust gases through in anauxiliary catalytic converter when the exhaust gases bypass the furtherimproved reverse flow catalytic converter.
 30. A method as claimed inclaim 23 further comprising a step of: actuating and resuming normalcontrol of the exhaust gas flow through the catalytic material in thecontainer when an instant temperature of the catalytic material dropsbelow the predetermined threshold.
 31. An improved valve structure for afurther improved reversing flow catalytic converter for exhaust gases,the further improved converter having a container which has a top endwith a first chamber and a second chamber which are in fluidcommunication with each other so that the exhaust gases introduced intoone of the first and second chambers flows through a catalytic materialin the container, comprising: an improved valve housing including animproved intake cavity, an improved exhaust cavity, a valve cavityextension to chamber one of the container and a valve cavity extensionto hamber two of the container, adapted to be mounted to the top end ofthe container, the improved intake cavity adapted for connection to anengine exhaust gas pipe of said engine and the improved exhaust cavitybeing adapted for connection to a tail pipe to permit egress of exhaustgases from said converter; an improved valve component for reversing gasflow operably mounted in the improved valve housing, adapted to be movedbetween a first position in which the improved intake cavitycommunicates with the first container chamber through its associatedextended valve cavity and the improved exhaust cavity communicates withthe second container chamber through its associated extended valvecavity and a second position in which the improved intake cavitycommunicates with the second container chamber through its associatedextended valve cavity and the improved exhaust cavity communicates withthe first container chamber through its associated extended valvecavity.
 32. An improved valve structure as claimed in claim 31 whereinthe improved valve housing includes two conjoined transverse walls thatdivide the cavity into four compartments that respectively form theimproved intake cavity, the improved exhaust cavity, the extended valvecavity to container chamber one and the extended valve cavity tocontainer chamber two.
 33. A valve structure as claimed in claim 32wherein the improved valve component includes: an improved valve flapperwhich is rotatably mounted to a bottom and a top plate of the valvehousing, and rotates about a central axis that is normal to the improvedvalve flapper, the improved valve flapper rotating between the twoconjoined walls defining the inlet and exhaust cavities and each of thetwo conjoined walls having a first opening and second openingtherethrough which communicate respectively with each of the chambers ofthe container through their associated extended valve cavities, and oneof the intake cavity and exhaust cavity of the valve housing.
 34. Animproved valve structure as claimed in claim 33 wherein the first andsecond chambers of the container are substantially semi-circular in planview and the bottom plate openings of the improved valve housing arealso substantially semi-circular in cross-section and oriented withoutoffset with respect to the container chambers. Each of the four openingsin the four wall sections of the two conjoined valve walls is positionedto communicate with only one of the container chambers through theirassociated extended valve cavities and one of the inlet or exhaustcavities when the valve flapper is in one of the first and secondpositions.
 35. An improved valve structure as claimed in claim 34wherein each of the openings in the improved valve conjoined wall systemis adapted to communicate with both the intake port and the exhaust portwhen the valve component is in the third position.
 36. An improved valvestructure as claimed in claim 35 wherein the flapper further comprises adrive shaft affixed to the central axis, extending axially through theimproved valve housing with one end projecting from the top of theimproved valve housing.
 37. An improved valve structure as claimed inclaim 36 wherein the improved valve housing further comprises amechanism for accurately positioning the valve housing on the top of thecontainer and removebly securing the same.
 38. An improved valvestructure as claimed in claim 37 wherein the semi-circular shape of theextended valve container port cavities and the semi-circular shape ofthe container chambers are substantially similar, and each of theopenings in the improved valve conjoined walls is slightly smaller thanhalf the area of the semi-circular cross-section of the extended valvecontainer ports in the bottom plate of the valve.
 39. An improved valvestructure as claimed in claim 38 further comprising a rotary actuatoroperablely associated with drive shaft at the projecting end, the rotaryactuator being adapted to override the improved center return mechanism.40. An improved valve structure as claimed in claim 39 wherein theimproved center return mechanism includes a four-spring system in whichuneven spring forces produce a torque adapted to rotate the drive shaftuntil the flapper is in the third position.
 41. An improved valvestructure as claimed in claim 39 wherein the improved valve componentincludes: an improved center return mechanism associated with theimproved valve component for moving the improved valve component to andmaintaining the improved valve component in a third position in whichexhaust gases are conveyed from the intake cavity to the exhaust cavitywithout passing through the catalytic material.
 42. A further improvedreversing flow catalytic converter incorporating the safeguard system asclaimed in one or more of claims 15-30.
 43. A further improved reversingflow catalytic converter incorporating the improved valve structure asclaimed in claims 31-37.
 44. A further improved revering flow catalyticconverter incorporating the improved valve structure as claimed in claim31, said further improved converter having a container that has a topend with a first chamber and a second chamber that are in fluidcommunication with each other so that the exhaust gases introduced intoone of the first and second chambers flow through a catalytic materialin the container and pass out of the container through the other secondor first chamber, is substantially described.
 45. A further improvedreversing flow catalytic converter as claimed in claim 1 wherein thecatalytic material is optionally a catalytic filter trap monolith
 46. Afurther improved reversing flow catalytic converter as claimed in claim45 wherein a fuel injector is affixed to a fuel manifold and diesel fuelis injected from the manifold into the container flow redirection bowland pulses fuel into the reactor core for vaporization with timeduration pulses provided from a controller with an algorithm that isbased on measuring monolith static temperature and on calculatingmonolith rate of temperature change and reacting to increase monolithtemperature by the addition of fuel when determined necessary asdictated by the algorithm.
 47. A further improved reversing flowcatalytic converter as claimed in claim 46 wherein the fuel injector ismounted on a manifold and the manifold also contains a fuel strainer andflow control orifice for restricting fuel flow and the manifold receivesa fuel supply from the low pressure fuel supply pump feeding the dieselinjector pump.
 48. A further improved reversing flow catalytic converteras claimed in claim 47 wherein the fuel injector is mounted on amanifold along with a purge air supply solenoid and check valveconnected such that when the engine is shut down, a pulse of vehicle airblows diesel fuel out of the injection line to prevent caking.
 49. Afurther improved reversing flow catalytic converter as claimed in claim45 wherein the catalytic material is optionally replaced by a filtermonolith without catalytic coating.
 50. A further improved reversingflow catalytic converter as claimed in claim 49 wherein a circularbottom plate is attached to the valve bottom and has two semi circularand diametrically opposed ports each subtended by an approximately 120degree angle of opening and the openings extend from near the bottomplate center, to the inner radius of the bottom plate with theorientation of the center line diameter bifurcating the center of thetwo 120 degree ports being at right angles to the container transversewall such that each port communicates only with one side of thecontainer as divided by the container transverse plate.
 51. A furtherimproved reversing flow catalytic converter as claimed in claim 50wherein the improved valve structure is mounted on the container in sucha way that a diametrical line bifurcating the two conjoined wallsdefining the inlet and exhaust cavities of said improved valve structureis at normal angle, as guided by positioning pins in the containerflange, to the container transverse wall.
 52. A further improvedcatalytic converter as claimed in claim 50 wherein an improved valveflapper combined with four rectangular openings in the four wallsections of the two conjoined valve walls is provided, said wallsseparated at an approximately 60 degree angle of opening from the centerof the valve and extending from the valve center to the valve outer wallin two diametrically opposed directions such that the flapper covers twoports when in either position one or position two and the valve portopenings optimally are sealed by the flapper with minimum leakage whenin cyclical operation and fully closed on either side.
 53. A furtherimproved reversing flow catalytic converter as claimed in claim 52wherein the improved valve flapper is adapted to be rotated by a normalshaft that is connected at the flapper along the shaft length, and atthe top end coupled to an electric stepper motor actuator that isattached to the improved valve structure and that rotates the valveflapper, as directed by the controller that activates the stepper motoractuator, to three operating positions, namely a position to permit:forward flow reverse flow bypass flow
 54. A further improved reversingflow catalytic converter as claimed in claim 53 wherein the steppermotor is a pneumatic stepper motor.
 55. A further improved reversingflow catalytic converter as claimed in claim 54 wherein a controllerprovides power to move and position the valve flapper in each of theoperating positions based on an algorithm embedded in the controller,the controller acting upon temperature measurements sent to it fromsensors embedded in the filter monolith.
 56. A safeguard system asclaimed in claim 16 for the further improved reversing flow catalyticconverter wherein the controller is adapted to move and position theimproved valve flapper to a bypass position and send a signal to anengine controller to adjust the fuel supply to the internal combustionengine when a rate of rise of the temperature of the filter monolith ishigher than a predetermined threshold retrieved from a look-up tableembedded in the controller.
 57. A safeguard system as claimed in claim56 for the further improved reversing flow catalytic converter whereinthe controller is adapted to move and hold the valve flapper to a bypassposition and send a signal to an engine controller to adjust the fuelsupply to an internal combustion engine when the temperature of thefilter monolith exceeds a third predetermined threshold.
 58. A safeguardsystem as claimed in claim 57 for the further improved reversing flowcatalytic converter further comprising an auxiliary catalytic converterconnected thereto for treating the exhaust gases only when the exhaustgases bypass the further improved reversing flow catalytic converter.59. A safeguard system as claimed in claim 57 for the further improvedreversing flow catalytic converter wherein during an overheating eventsaid system will cause power to be blocked from the fuel injector by aninterlock between the controller and injector valve.
 60. An improvedvalve structure as claimed in claim 37 wherein the semi-circular shapeof the container cavities extends over a 180 degree angle and thesemi-circular shape of the valve bottom plate openings extends over a120 degree angle, and each of the openings in the valve walls isslightly smaller than half the area of the semi-circular cross-sectionof each valve bottom plate port, the openings in the walls beingoriented at an angle of about 60 degrees with respect to each other,this being the flapper travel zone.